Archive for October, 2020

Crons in AWS Elastic Beanstalk

October 23, 2020

It’s as easy as adding the following to your .ebextensions folder:

files:
"/usr/local/bin/acronjob.sh":
mode: "000755"
owner: root
group: root
content: |
#!/bin/bash
root . /command/to/run

Running a cron on one server?

files:
"/usr/local/bin/test_cron.sh":
mode: "000755"
owner: root
group: root
content: |
#!/bin/bash
INSTANCE_ID=`curl http://169.254.169.254/latest/meta-data/instance-id 2>/dev/null`
REGION=`curl -s http://169.254.169.254/latest/dynamic/instance-identity/document 2>/dev/null | jq -r .region`

# Find the Auto Scaling Group name from the Elastic Beanstalk environment
ASG=`aws ec2 describe-tags --filters "Name=resource-id,Values=$INSTANCE_ID" \
--region $REGION --output json | jq -r '.[][] | select(.Key=="aws:autoscaling:groupName") | .Value'`

# Find the first instance in the Auto Scaling Group
FIRST=`aws autoscaling describe-auto-scaling-groups --auto-scaling-group-names $ASG \
--region $REGION --output json | \
jq -r '.AutoScalingGroups[].Instances[] | select(.LifecycleState=="InService") | .InstanceId' | sort | head -1`

# If the instance ids are the same exit 0
[ "$FIRST" = "$INSTANCE_ID" ]

"/usr/local/bin/acronjob.sh":
mode: "000755"
owner: root
group: root
content: |
#!/bin/bash
/usr/local/bin/test_cron.sh || exit
root . /command/to/run

Crons not running on Amazon Linux?

When placing cronjobs in /etc/cron.d do not use dots or hyphens in the file name.